Electromagnetic stepping mechanism



Feb. 10, 1953 D. E. HOOKER 2,627,755

ELECTROMAGNETIC STEPPING MECHANISM Filed Oct. 24, 1951 Patented Feb. 10, 1953 ELECTROMAGNETIC STEPPIN G MECHANISM Donald E. Hooker, Skokie, Ill., assignor to Raymond T. Moloney, Chicago, 111.

Application October 24, 1951, Serial .No. 252,858

2 Claims. 1

This invention pertains to electromagneticallyactuated stepping mechanism of the pawl and ratchet class, and has as its principal object the provision of a high-speed stepping mechanism for use with devices of this class.

It is a further and more specific object to provide a stepping mechanism of the class described, which is relatively economical to make, which is simple and reliable in construction and-operation, and which includes as a feature thereof several driving pawls actuated by a single solenoid and spring means to step a single ratchet disc at increased speed by reason of the driving action of all pawls at some phase of each complete operating stroke or cycle of the driving solenoid or other driving means.

A further specific object is the provision, in a device of the class described, of means including twin stepping pawls actuated in concert by a single solenoid to move relative to a ratchet wheel so that the wheelis advanced by one pawl on the initial stroke of the solenoid, and the wheel is againadvanced by the other pawl on the return stroke of the solenoid, so that the rate of stepping advance of the wheel is multiplied for each operatin cycle of the awl means.

A further object is to provide a stepping mechanism which moves the ratchet wheel in a more nearly continuous motion when the pawl means is rapidly actuated.

Another object is the provision of an indexing or indicating mechanism of the pawl-and-ratchet stepping type which includes a ratchet wheel driven in consecutive steps by two co-reciprocable pawls, each of which steps the wheel once, sequentially, for each complete reciprocatory and joint travel of the two pawls, together with a sweep index arm rotatable with the wheel and lodged into uniformly spaced, successive positions of rest which are at least two steps apart about the arc of travel of said arm.

Additional objects and aspects of novelty and utility relate to details of the construction and operation of the illustrative embodiment described hereinafter in View of the annexed draw- I ing, in which:

Fig. 1 is a front elevation of the novel stepping mechanism;

Fig. 2 is a top plan View of the device shown in Fig. 1;

Fig. 3 is a fragmentary rear elevation of the stepping mechanism disclosing a rotary signal driven thereby;

Fig. 4 is a fragmentary front elevational detail showing the driving pawls in the advancing phase of the power stroke.

Referring to Fig. 1, the stepping mechanism is shown mounted on a base plate It adapted to stand upright on base flange I l.

Driving or actuating means for the mechanism includes an electromagnetic solenoid or coil l2 having a plunger 23 reciprocable therein, mounted on the plate by means of brackets l4, and adapted to be energized by connections with conductors It in any desired control circuit (not shown).

The member to be stepped or driven is a ratchet wheel is rotatably mounted on a stud shaft l9 journaled in the base plate.

Dual-acting stepping means includes a pair of pawls 2t and 2! each pivotally connected at 20A and MA with a corresponding link 253 or 2IB, said links each being pivotally mounted on the base plate on pin means 23, the two links also having their respective inner ends pivotally connected at 24 to the solenoid plunger 13, such that reciprocable movements of said plunger impart simultaneous rocking motions to the links, with a consequent simultaneous reciprocation of the two driving pawls 2E3 and 2 i.

The pawls are yieldingly urged toward each other by a linking spring 25 stretched between pins on each pawl, so that the offset nose portions 29X and ZlX thereof are normally urged into the ratchet teeth ISX.

A normalizing spring 26 has one end anchored on a pin 21 in the base plate, and its other end attached to one of the pawl-link pivot connections 2IA, and acts to rock the link 2IB clockwise (Fig. 1), so that the solenoid plunger 13 is normally withdrawn thereby, andthe two pawls are disposed in a normal starting positionrelative to the ratchet wheel 18.

It is important to observe in Fig. 1 that the pitch of the ratchet teeth presented to the pawls is reversed by reason 0 the engagement of the pawls on opposite sides of the pivotal center of the wheel.

As a result of the aforesaid opposite pitching, it will beclear that when the pawls advance from the normal position shown in Fig. 1 to the advanced position of Fig. t (with solenoid plunger I3 attracted) the pawl 2| will have advanced the ratchet disc a distance of one tooth by pushing against the particular tooth I8XY, whereas the other pawl 20 will have slipped past the particular tooth I8XZ.

It is also important to observe that in the latter slipping action of pawl 20 over tooth lBXZ, the said tooth was moved backward toward the pawl 20 and its nose 20X, concurrently with the advancing motion of the pawl 20 toward said backratchet wheel on the advancing movement of the first pawl 2|; a positive advance of the second pawl 20 past the tooth |8XZ later to be driven thereby; a time interval for positive completion of the first power stroke and step and positioning of the second pawl for its power stroke; and finally, a momentary no-load condition for the second pawl 20 during which it can overcome its reverse-travel inertia and gain some momentum in the return direction before loading by driving engagement with tooth |8XZ on the return travel, it being noted that this return travel and working power is eifected by the normalizing spring 26, and it is desirable that this spring shall be strong enough to do the necessary work on the return stroke, on one hand, and yet not over- 1y strong to load the system unnecessarily on the initial advancing stroke of pawl 2|.

The stroke of the pawl system is limited in the return direction by a stop in the form of set screw 28 (Fig. 1) mounted in a bracket 2'! on the base plate, and positioned to be engaged by part of the pawl-link pivotal connection at 20A. In the opposite direction, it is satisfactory to have the inward stopping position of plunger i3 in coil l2 effect the limiting travel for the forward or initial advancing stroke of the pawls.

Such a stepping mechanism is useful in many applications, for example, in connection with rotary switches; to actuate signals or a scoreregister or totalizer device, such as shown in Figs. 2 and 3.

As depicted in Fig. 2, the shaft I9 has fixed thereon a metal arm 30 having attached to its end a socket 3| carrying a small sweep lamp 32. The socket shell 3| may be grounded to said arm and have its remaining terminal connected by a .conductor 33 to the metal annulus 34 of a commutator ring fixed between two larger annular insulating rings 35. A spring wiper contact rides between the discs 35 on ring 36 and completes an energizing circuit (not shown) for the movable lamp.

The stepping mechanism steps the arm 39 to position the lamp 32 before circularly arranged indicia (Fig. 3) 3'! arranged on an opaqued panel -38 situated before the aforesaid sweep lamps.

The panel 38 has been simplified to display only a few illustrative number indications 31, but it.

will be apparent that the stroke of the pawls and ,the number and spacing of the ratchet teeth ISX may be modified to yield a greater or lesser range of steps, and gearing may be interposed (not shown) between the drive shaft l9 and the arm 30, or other driven means, to extend the stepping range. as desired.

By selecting a solenoid plunger structure and pawl mechanism of suitable minimized weight,

the travel of the arm 30 may be made so rapid as to appear continuous rather than discontinuous, On the other hand, by holding the coil i2 energized, the arm 30, and hence the lamp or other device 32 can be stopped intermediate any two normal positions, as for example between the indications IE0 and 280, etc., in such instance, giving no signal through the opaque panel 38.

The described construction clearly doubles the stepping speed of the ratchet system since each complete reciprocation or stroking of the solenoid plunger i3 effects two steps of the wheel l8; and it will also be apparent that rapid reciprocation of the plunger thereby eifects a more nearly continuous rotative motion of the wheel, while at the same time undesirable loading by the spring 26 and the relatively idle pawl 20 is minimized during the working stroke of the other pawl 2| owing to the aforesaid overtravel provisions, the converging spring 25 being relatively light and just strong enough to assure positive engagement and following-action of the pawl noses into the teeth.

The disclosed construction lends itself to both heavy-working applications and light-duty but high-speed applications for more delicate types of switching or other working applications, yet it is sufiiciently simple and rugged to afford reliable operation in both types of application.

I claim:

1. In a high-speed stepping mechanism, a toothed rotatable ratchet wheel, a pair of pawls each drivingly engaging the wheel teeth on 0pposite sides of the axis of the wheel, a spring attached to both pawls to yieldingly urge the same into said teeth, a solenoid mounted with its bore extending normally of said axis in alignment therewith, a solenoid plunger reciprocable in said bore in between said pawls, a pair of links each having one end pivotally connected to an end region of one of said pawls remote from said wheel, said links each having their opposite and remaining end portions connected to a common pivot point on the outer end of said plunger, each said link having a fixed pivotal mounting at a point in between its connection to a pawl and to said common pivot, a second spring means having connection to the region of pivotal connection of a first one of said links with one of said pawls and urging the said link in a direction to withdraw the plunger from said bore to a normal position, and adjustable stop means positionable to be engaged by the region of pivotal connection of the second one of said links with the corresponding pawl to limit the withdrawal of said plunger to said normal position, reciprocation of the plunger by intermittent energization of the solenoid and action of said second spring mean effecting reciprocatory motion of the pawls to step the wheel twice for each reciprocation of the plunger.

2. In a two-step per cycle ratchet stepping mechanism of the known type which includes a rotatable ratchet wheel with a pair of jointlyreciprocable stepping pawls, each of which is located to engage the ratchet teeth on respectively diametric sides of the wheel axis, improvements comprising, to wit: a high-speed pawl means including a solenoid having its bore extending in alignment with, and normally of, the wheel axis; a plunger reciprocable in said bore; a pair of contiguous links extending in opposite lateral directions of said plunger with contiguous ends pivotally connected to an end of said plunger; each said link having an opposite and outer end part pivotally connected to an end of one of said pawls; said links each having a pivot between its ends which is parallel to the wheel axis; spring means drawing the ratchet ends of the pawls respectively toward each other and into said teeth; spring means having connection with said pawl 5 means to pivotally dispose the contiguous ends UNITED STATES PATENTS of said pawls outwardly of the solenoid bore to Number Name Date withdraw said plunger; means for limiting the 2217 381 Allen Oct 15, 1940 reciprocable stroke of said pawl means; and at Obszamy 13, 1942 least one of said pawls having an over-stroke to 5 2365547 Hausherr 19' 1944 reduce the loading thereof on the wheel.

DONALD E. HOOKER. FOREIGN PATENTS Number Country Date REFERENCES CITED 983,506 France June 25, 1951 The following references are of record in the 10 file of this patent: 

